Heat sealed pull tab



Oct. 28, 1969 s. D. COLLIE 3, 75,24

HEAT SEALED PULL TAB Original Filed Nov. 2, 1964 3 Sheets-Sheet 1 FIG.

INVENTOR. S. D. COLLIE A 7' TORNE KS Oct. 28, 1969 s. o. COLLIE 3,475,246

HEAT SEALED PULL TAB Original Filed Nov. 2, 1964 3 Sheets-Sheet INVENTOR. s. D. COLLIE BY I A 7" TOR/VEYS 1969 s. D. COLLJE 3,,475246 HEAT SEALED PULL TAB I Original Filed Nov. 2, 1964 3 Sheets-Sheet Z lLl/I/I/I/I/I/l/l/l/I //I l l// I [/1] F G 3d INVENTOR. S. D. COLL! E A TTORNEYS United. States. Patent 3,475,246 p 'HEAT SEALED PULL TA Stafford D. Collie, Kansas City,' Mo., assignor to Phillips Petroleum Company, a corporation of Delaware Original application Nov. 2, 1964,,Ser. No. 408 ,2 81, now a Patent N0.r3,321,123, dated May 23, 1 967. Divided and this application Feb. 20, 1967, Ser..No. 617,405

. Int. Cl. B2'9c 27/06; B321) 31/20 applying pressure to the pull tab; heating the bottom survface of the plastic lid thereby causing the pull tab to be heat-sealed to the lid. The tab can be key-shaped thus producing a key-shaped opening in the lid when the tab is removed. I

This is a division of application Ser. No. 408,281, filed Nov. 2, 1964, now Patent No. 3,321,123.

The present invention relates to sealed thermoplastic containers. In one aspect it relates to those thermoplastic containers which can be opened to permit the removal of the contents Without requiring the use of special implements. In another aspect, the invention relates to a heat-sealed pull tab which may be applied to the top of said container whereby the tab forms a shaped opening in the lid when it is peeled therefrom. In yet another aspect, the invention relates to thermoplastic containers .which are opened by tearing a plastic pull tab material along a predetermined line or region without the need of .any implement or tool. In yet another aspect this invention relates to a novel method for applying a pull tab to the lid of the container whereby the pull tab will form an opening in the lid when it is pulled or peeled therefrom.

In recent years there has been a trend toward the packaging of solid and liquid materials in thermoplastic containers. Suchcontainers-are more commercially desirable 1111311111086 containers previously made from cardboard, paper, metal and the like in that they can be molded into attractive shapes. These thermoplastic containers are formed with the lid produced separately from the body of the container, and after the body of the container is filled with a particular type of liquid material, the plastic lid is then applied by known heat-sealing methods to the open end of the container. In order to provide access to the contents of the container, it was necessary to be able to punch a hole in the plastic lid. Pull or rip tabs have been extensively used in forming such holes in the tops of metal containers; however, when this means was employed for plastic containers, the prior art experienced considerable difficulty in its attempt to provide a satisfactory tab opener which'eifected a rupturing or tearing of a hole in the plastic lid rather than the tab itself.

Moreover, the tab, although readily and conveniently removed merely by lifting or peeling it from the plastic lid, had to be sufficiently rugged towithstand the temperatures and treatment to. which said merchandise would be subjected so as not to cause a leak in the container.

One of the objectssof the present invention is to provide a novel pull tab opening means for thermoplastic containers which effects a rupturing or tearing of the hole in the plastic container rather than in the tab itself.

Another object is to provide a method of making a' package or container of thermoplastic material embodying novel means for enabling a person to readily open the package.

Yet another object of the invention is to provide a method for applying a pull tab to a thermoplastic lid for a container whereby the pull tab fills a shaped opening in the lid of the container, thereby making it possible to maintain a hermetic seal within the container.

A further object of the invention is to provide a novel method of making a unique form of pull tab which is suitable for application to containers made from thermoplastic materials, and to provide such a method which can be used in conjunction with the application of the pull tab itself to the plastic container.

A further object of the invention is the provision of a novel heat-sealed pull tab for producing an opening in a plastic container lid positively and expeditiously which results in requiring the expenditure of a minimum of effort on the part of the user in lifting the tab and pulling the same off the container wall.

A still further object of the present invention is the provision of a heat sealed pull tab which is made an integral part of a plastic lid portion of a container and the lid portion is sealed to the container with the pull tab attached thereto.

A still further object of the present invention is to provide a thermoplastic container having a seal, although readily and conveniently removed merely by lifting or peeling off the tab in the manner aforesaid, sufficiently rugged to withstand the temperatures and treatment to which such merchandise is ordinarily subjected.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description which is considered in connection with the accompanying drawings wherein:

FIGURE 1 shows a diametric view of the container of the present invention as it would be merchandised;

FIGURE 2 shows a view similar to FIGURE 1 i1- lustrating the removal of the pull tab from the lid of the container;

FIGURES 3a to 3d illustrate by way of example, the steps of the process of the subject invention in securing the pull tab to the lid of the container;

FIGURE 4 shows a diametric view of the underside of the pull tab after it has been removed from the lid;

FIGURE 5 shows a diametric view of the lid showing another embodiment in the method of securing the tab thereto.

This invention teaches a novel method for applying a pull tab to a plastic lid for a container in such a manner that the plastic in that portion of the lid immediately beneath the tab is structurally weakened so that it will adhere to the tab upon the tab being peeled or pulled from the top surface of the lid whereby an opening is conveniently formed in the top of the container.

The invention will be described hereinafter as applied to a bag or container having at least its lid portion consisting of thermoplastic material, but it will be understood by those skilled in the art that the pull tab of the invention can be applied to a wrapper for any object, regardless of size or shape.

More particularly in describing the invention, in FIG- URE l, is shown a container 1 comprising a body 3 and a lid 5. The container may be made of any suitable flexible thermoplastic material, such as a vinyl plastic or polyethylene, or other polymeric, plastic material, or of a paper material coated with a flexible thermoplastic coating.

A thermoplastic pull tab 7 is sealed to the lid 5 with heat and pressure according to a process hereinafter described. Although the pull tab may take various shapes,

the key hole shape represented in the drawings is preferred. The body of the pull tab is formed near the pe-- riphery of the lid with a curved edge 9a defining the face thereof, and an elongated edge 9b extending from this curved edge toward the center of the lid. This edge 9b facilitates the removal of the tab from the lid. The lid should be sufiiciently flexible to permit the tab to be lifted away from the surface of the lid and to permit the tab to be peeled ofi; however, it is also desired that it have sufficient firmness and toughness to form a rigid cover for the container capable of withstanding really rugged handling.

One method which may be used for carrying out the invention is that described in FIGURES 3a and 3d, in which there is shown a rubber mat 10 having a raised nipple 12 integral therewith, the nipple is substantially of the same design as the opening in the lid 5. A steel ruled die 11 in this preferred embodiment takes the shape of a key hole having a sharp curved edge 11a defining the base thereof and an elongated edge 11b extending therefrom. This steel rule die is then glued to the rubber mat in such a manner that the die surrounds the nipple causing it to protrude above the edges of the steel die. The plastic tab 7 is then centered over the steel die and the topside of the plastic lid is then centered over the pull tab as shown in FIGURE 3.

A Teflon covered heating head 13 having a source of heat (not shown) is applied to the under side of the plastic lid 5. This lid is then pressed down onto the rubber mat causing the rubber nipple which extends above the edges of the steel die, to become compressed thereby pushing the tab against the top side of the lid which has been weakened by the application of heat on its under side from the head 13. This action of heat and pressure bonds the tab to the lid. At the same time the lid comes into contact with the sharp edges 11a and 11b of the die 11 which causes the plastic lid to be weakened structurally along the contour of these edges. As a result the bond between the tab and the lid is stronger than that portion of the plastic lid which comes into contact with the sharp edges of the aforesaid die. Another important feature of this invention is that the heat is applied to the under side of the lid. Thus even if the container lid and the tear tab are of the same material and of the same thickness, the lid, not the tab, will tear because it receives more heat and is preferentially softened. By varying the amount of heat and pressure, it is possible to control the amount of pull required to remove the tab from the lid. The more heat and pressure, the easier it becomes to remove the tab. The temperature applied depends on the melting point of the polymer; however, the temperature can be raised considerably if the time and pressure variables are reduced.

For example, a tab of 18 mils thickness was heat sealed to a lid of 13 mils thickness at a temperature of 250 F. with a pressure of approximately 100 pounds/ square inch and a dwell time of 1 /2 seconds was suitable.

It is to be noted that the pull tab of the subject invention differs from the tear strip method of opening thermoplastic bags in that the tear strip must be of a heavier and stronger material than the bag itself whereas the effectiveness of the subject invention is dependent upon the heat and pressure, not the thickness of material used. It is possible to employ a tab being considerably lighter and weaker than the material from which the lid is made.

When the pull tab has been heat sealed to the lid as set forth hereinabove, the lid may be applied to the container according to conventional methods. When it is desired to open the container to provide access to the contents, the tab 7 is lifted away from the surface of the t" lidS along the edge 9b and then grasped with the fingers and peeled off.

The lid, having been previously weakened along a line which followed the contour of the edges of the die used in applying the tab to the lid, is fractured along this line so that as a result that portion of the lid sealed to the tab remains intact therewith and leaves an opening in the tape of a key on the lid. Because of the manner in which this tab was applied to the lid, its removal occurs cleanly without forming jagged edgesaround the key hole.

In another embodiment (see FIGURE 5) one end 15 of tab 7 is positioned over the nipple 12. Heat and pressure are once more applied to the lid 5 as described hereinabove so that only the end 15 of the tab 7 is sealed to the lid. When this tab 7, after being sealed in this manner, is pulled from the lid it will pull that portion of the lid which has been weakened by the heat and pressure through the combined action of die 11 and nipple 12 along with it, thereby creating an opening in the lid.

In the foregoing, the invention has been described with reference to a specific illustrative device and method. It will be evident, however, that modifications and variations, as well as the substitution of equivalent elements and steps of those described for illustration, may be made without departing from the broader scope and spirit of the invention as defined by the appended claims. Specification and drawing are to be regarded in an illustrative rather than a restrictive sense.

I claim:

1. A process for forming an opening in the thermoplastic lid, comprising the steps of bringing a pull tab also consisting of a thermoplastic material in contact with a portion of the plastic lid on the top surface thereof; applying pressure to the top surface of said portion of the lid; applying heat to the bottom surface of said portion of the lid, thereby causing the pull tab to be heat sealed to the said portion of the lid and also causing the said portion of the lid to become sufiiciently structurally weakened so that when the pull tab is removed this portion of the lid will remain attached to the pull tab and thereby cause an opening to be made in the lid.

2. The process according to claim 1 wherein said lid and said tab are polyethylene, said tab having the shape of the desired opening and said pressure is applied directly to said pull ta'b as'heat is applied directly to the bottom surface of the lid thereby causing the pull tab to be heat sealed to the said portion of the lid and causing the said portion of the lid to be sufficiently structurally weakened along the outer periphery of said pull tab.

3. The process according to claim 2 wherein said pull tab is key shaped and said pressure is applied along a line forming a closed key-shaped loop.

4. A process according to claim 1 wherein a heating head having a heat source is applied to the under side of said plastic lid, applying pressure to said lid to cause said lid to be pressed down onto a mat; compressing the tab against the top side of the lid which has been softened and weakened by the application of heat on its under side by said heating head thereby bonding said tab to said lid.

5. The process according to claim 1 wherein said pressure directly applied to said pull tab is about pounds per square inch and said heat applied to the bottom surface of said lid is about 25 0 F. 7

References Cited UNITED STATES. PATENTS DOUGLAS J. DRUMMOND, Primary Examiner 

1. A PROCESS FOR FORMING AN OPENING IN THE THERMOPLASTIC LID, COMPRISING THE STEPS OF BRINGING A PULL TAB ALSO CONSISTING OF A THERMOPLASTIC MATERIAL IN CONTACT WITH A PORTION OF THE PLASTIC LID ON THE TOP SURFACE THEREOF; APPLYING PRESSURE TO THE TOP SURFACE OF SAID PORTION OF THE LID; APPLYING HEAT TO THE BOTTOM SURFACE OF SAID PORTION OF THE LID, THEREBY CAUSING THE PULL TAB TO BE HEAT SEALED TO THE SAID PORTION OF THE LID AND ALSO CAUSING THE SAID PORTION OF THE LID TO BECOME SUFFICIENTLY STRUCTURALLY WEAKENED SO THAT WHEN THE PULL TAB IS REMOVED THIS PORTION OF THE LID WILL REMAIN ATTACHED TO THE PULL TAB AND THEREBY CAUSE AN OPENING TO BE MADE IN THE LID. 